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//=================================================================================================
/*!
// \file blaze/util/EnableIf.h
// \brief Header file for the EnableIf class template
//
// Copyright (C) 2013 Klaus Iglberger - All Rights Reserved
//
// This file is part of the Blaze library. You can redistribute it and/or modify it under
// the terms of the New (Revised) BSD License. Redistribution and use in source and binary
// forms, with or without modification, are permitted provided that the following conditions
// are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
// of conditions and the following disclaimer in the documentation and/or other materials
// provided with the distribution.
// 3. Neither the names of the Blaze development group nor the names of its contributors
// may be used to endorse or promote products derived from this software without specific
// prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
// SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
// TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
// DAMAGE.
*/
//=================================================================================================
#ifndef _BLAZE_UTIL_ENABLEIF_H_
#define _BLAZE_UTIL_ENABLEIF_H_
namespace blaze {
//=================================================================================================
//
// CLASS DEFINITION
//
//=================================================================================================
//*************************************************************************************************
/*!\brief Substitution Failure Is Not An Error (SFINAE) class.
// \ingroup util
//
// The EnableIfTrue class template is an auxiliary tool for an intentional application of the
// Substitution Failure Is Not An Error (SFINAE) principle. It allows a function template or a
// class template specialization to include or exclude itself from a set of matching functions
// or specializations based on properties of its template arguments. For instance, it can be
// used to restrict the selection of a function template to specific data types. The following
// example illustrates this in more detail.
\code
template< typename Type >
void process( Type t ) { ... }
\endcode
// Due to the general formulation of this function, it will always be a possible candidate for
// every possible argument. However, with the EnableIfTrue class it is for example possible to
// restrict the valid argument types to built-in, numeric data types.
\code
template< typename Type >
typename EnableIfTrue< IsNumeric<Type>::value >::Type process( Type t ) { ... }
\endcode
// In case the given data type is not a built-in, numeric data type, the access to the nested
// type defintion \a Type of the EnableIfTrue template will fail. However, due to the SFINAE
// principle, this will only result in a compilation error in case the compiler cannot find
// another valid function.\n
// Note that in this application of the EnableIfTrue template the default for the nested type
// definition \a Type is used, which corresponds to \a void. Via the second template argument
// it is possible to explicitly specify the type of \a Type:
\code
// Explicity specifying the default
typename EnableIfTrue< IsNumeric<Type>::value, void >::Type
// In case the given data type is a boolean data type, the nested type definition
// 'Type' is set to float
typename EnableIfTrue< IsBoolean<Type>::value, float >::Type
\endcode
// For more information on the EnableIfTrue/EnableIf functionality, see the Boost library
// documentation of the enable_if family at:
//
// \a http://www.boost.org/doc/libs/1_60_0/libs/utility/enable_if.html.
*/
template< bool Condition // Compile time condition
, typename T=void > // The type to be instantiated
struct EnableIfTrue
{
//**********************************************************************************************
typedef T Type; //!< The instantiated type.
//**********************************************************************************************
};
//*************************************************************************************************
//*************************************************************************************************
/*! \cond BLAZE_INTERNAL */
/*!\brief EnableIfTrue specialization for failed constraints.
// \ingroup util
//
// This specialization of the EnableIfTrue template is selected if the first template parameter
// (the compile time condition) evaluates to \a false. This specialization does not contains a
// nested type definition \a Type and therefore always results in a compilation error in case
// \a Type is accessed. However, due to the SFINAE principle the compilation process is not
// necessarily stopped if another, valid instantiation is found by the compiler.
*/
template< typename T > // The type to be instantiated
struct EnableIfTrue<false,T>
{};
/*! \endcond */
//*************************************************************************************************
//*************************************************************************************************
/*!\brief Auxiliary type for the EnableIfTrue class template.
// \ingroup util
//
// The EnableIfTrue_ alias declaration provides a convenient shortcut to access the nested \a Type
// of the EnableIfTrue class template. For instance, given the type \a T the following two type
// definitions are identical:
\code
using Type1 = typename EnableIfTrue< IsBuiltin<T>::value >::Type;
using Type2 = EnableIfTrue_< IsBuiltin<T>::value >;
\endcode
*/
template< bool Condition // Compile time condition
, typename T=void > // The type to be instantiated
using EnableIfTrue_ = typename EnableIfTrue<Condition,T>::Type;
//*************************************************************************************************
//=================================================================================================
//
// CLASS DEFINITION
//
//=================================================================================================
//*************************************************************************************************
/*!\brief Substitution Failure Is Not An Error (SFINAE) class.
// \ingroup util
//
// The EnableIf class template is an auxiliary tool for an intentional application of the
// Substitution Failure Is Not An Error (SFINAE) principle. It allows a function template
// or a class template specialization to include or exclude itself from a set of matching
// functions or specializations based on properties of its template arguments. For instance,
// it can be used to restrict the selection of a function template to specific data types.
// The following example illustrates this in more detail.
\code
template< typename Type >
void process( Type t ) { ... }
\endcode
// Due to the general formulation of this function, it will always be a possible candidate
// for every possible argument. However, with the EnableIf class it is for example possible
// to restrict the valid argument types to built-in, numeric data types.
\code
template< typename Type >
typename EnableIf< IsNumeric<Type> >::Type process( Type t ) { ... }
\endcode
// In case the given data type is not a built-in, numeric data type, the access to the nested
// type defintion \a Type of the EnableIf template will fail. However, due to the SFINAE
// principle, this will only result in a compilation error in case the compiler cannot find
// another valid function.\n
// Note that in this application of the EnableIf template the default for the nested type
// definition \a Type is used, which corresponds to \a void. Via the second template argument
// it is possible to explicitly specify the type of \a Type:
\code
// Explicity specifying the default
typename EnableIf< IsNumeric<Type>, void >::Type
// In case the given data type is a boolean data type, the nested type definition
// 'Type' is set to float
typename EnableIf< IsBoolean<Type>, float >::Type
\endcode
// Note that in contrast to the EnableIfTrue template, the EnableIf template expects a type as
// first template argument that has a nested type definition \a value. Therefore the EnableIf
// template is the more convenient choice for all kinds of type traits.
//
// For more information on the EnableIfTrue/EnableIf functionality, see the Boost library
// documentation of the enable_if family at:
//
// \a http://www.boost.org/doc/libs/1_60_0/libs/utility/enable_if.html.
*/
template< typename Condition // Compile time condition
, typename T=void > // The type to be instantiated
struct EnableIf : public EnableIfTrue<Condition::value,T>
{};
//*************************************************************************************************
//*************************************************************************************************
/*!\brief Auxiliary alias declaration for the EnableIf class template.
// \ingroup util
//
// The EnableIf_ alias declaration provides a convenient shortcut to access the nested \a Type
// of the EnableIf class template. For instance, given the type \a T the following two type
// definitions are identical:
\code
using Type1 = typename EnableIf< IsBuiltin<T> >::Type;
using Type2 = EnableIf_< IsBuiltin<T> >;
\endcode
*/
template< typename Condition // Compile time condition
, typename T=void > // The type to be instantiated
using EnableIf_ = typename EnableIf<Condition,T>::Type;
//*************************************************************************************************
} // namespace blaze
#endif
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